Medications such as Ozempic, Wegovy, Mounjaro, and Zepbound have become household names in recent years.
Originally developed to help people with type 2 diabetes control their blood sugar levels, these drugs later gained enormous attention because of their ability to help people lose significant amounts of weight. Millions of people now use them, and doctors continue to discover new ways these medications may affect health.
Now, a new study suggests that these popular drugs may provide another unexpected benefit. Researchers found that women taking GLP-1 medications were significantly less likely to develop breast cancer than women who were not taking the drugs.
The findings were presented at the 2026 American Society of Clinical Oncology Annual Meeting and were also published in JCO Oncology Practice. The research was led by Dr. Elizabeth McDonald, a professor of Radiology at the University of Pennsylvania Perelman School of Medicine and a breast radiologist at the Abramson Cancer Center.
Breast cancer remains one of the most common cancers affecting women around the world. According to health experts, millions of women are diagnosed with the disease each year. While screening programs and treatments have improved survival rates dramatically over the past few decades, preventing breast cancer before it starts remains a major challenge.
Current prevention options are limited. Some women with inherited genetic mutations choose preventive surgery to reduce risk.
Others may take medications such as tamoxifen, which can lower breast cancer risk but may also cause side effects that discourage many women from using it. Because of this, scientists are constantly searching for safer and more practical ways to prevent the disease.
GLP-1 medications work by copying a natural hormone called glucagon-like peptide-1. This hormone helps regulate blood sugar levels and reduces appetite.
As a result, many people feel full sooner and eat less, leading to weight loss. Semaglutide-based drugs include Ozempic and Wegovy, while tirzepatide-based medications include Mounjaro and Zepbound.
Researchers reviewed electronic health records from 111,646 women between the ages of 45 and 80 who had a body mass index of 25 or higher and had undergone breast imaging through the Penn Medicine health system between January 2022 and June 2025.
Among these women, more than 15,000 had prescriptions for GLP-1 medications. The remaining women had not used these drugs. The researchers then compared breast cancer diagnoses between the two groups.
To make the comparison as fair as possible, the team created a second analysis in which each woman taking a GLP-1 drug was matched with a similar woman who was not taking one. Factors such as age, race, ethnicity, body weight, breast density, and diabetes status were considered.
The results were striking. In the overall study population, women taking GLP-1 medications had about 35 percent lower odds of developing breast cancer. In the matched analysis, the reduction remained strong at about 30 percent.
The consistency of the findings made researchers take notice. Although the study cannot prove that the medications directly prevented cancer, it adds to a growing body of evidence suggesting that GLP-1 drugs may influence cancer-related biological processes.
Scientists believe several factors could explain the findings. One obvious explanation is weight loss. Excess body weight, especially after menopause, is a well-known risk factor for breast cancer. By helping women lose weight, GLP-1 drugs may indirectly reduce cancer risk.
However, researchers suspect there may be more to the story. Previous studies have shown that GLP-1 medications can reduce chronic inflammation throughout the body. Long-term inflammation has been linked to cancer development. These drugs also affect metabolism and may influence biological pathways involved in cell growth and gene regulation.
The researchers noted several limitations. They did not separate the results by individual drugs, so it remains unclear whether Ozempic, Wegovy, Mounjaro, and Zepbound have similar effects. They also did not examine treatment duration, inherited cancer risk, cancer stage, or tumor type.
Because of these unanswered questions, the research team is planning larger clinical trials involving women at high risk of breast cancer. Such studies are needed to determine whether the medications truly reduce cancer risk or whether other factors are responsible for the association.
The findings are exciting because they suggest that a class of drugs already being used by millions of people might one day help prevent a disease that affects millions more.
If you care about breast cancer, please read studies about how eating patterns help ward off breast cancer, and soy and plant compounds may prevent breast cancer recurrence.
For more health information, please see recent studies about how your grocery list can help guard against caner, and a simple way to fight aging and cancer.
Source: University of Pennsylvania.
